Conventionally, epoxy resin compositions have been widely used for components of electrical and electronic equipment, automobile parts, aircraft parts, construction materials, and so forth because of excellent adhesive force to various members and excellent durability. However, cured products of such epoxy resin compositions used in adhesives are hard and brittle, and hence easily broken when impact is applied thereto. For this reason, studies have been conventionally conducted to impart toughness by adding elastomer components or using elastomer-modified epoxy resins without deteriorating the basic properties of the epoxy resins.
Patent Literature 1 describes an epoxy resin composition usable as adhesion for structure and containing an epoxy resin, a rubber-modified epoxy resin, a urethane resin in which the terminal isocyanate of the urethane prepolymer is blocked, and a curing agent.
Patent Literature 2 describes an adhesive for automobile structure, which contains an epoxy resin, a urethane-modified epoxy resin, a NBR-modified epoxy resin, a NBR-rubber-particle dispersed epoxy resin, and a latent curing agent.